<!DOCTYPE html>
<html lang='en'>

<head>
    <meta charset='UTF-8' />
    <meta name='viewport' content='width=device-width, initial-scale=1.0' />
    <title>Document</title>
    <script src='../js/vue.js'></script>
</head>
<!-- 
            监视属性watch
                1.当被监视的属性变化时，回调函数自动调用，进行相关操作
                2.监视的属性必须存在，才能进行监视！！
                3.监视的两种写法
                    (1).new Vue时传入watch配置
                    (2).通过vm.$watch进行监视
         -->

<body>
    <div id='root'>
        <h2>今天天气很{{info}}</h2>
        <br>
        <button @click="changeWeather">切换天气</button>
    </div>
    <script>
        const vm = new Vue({
            el: '#root',
            data: {
                isHot: true,
                number: {
                    a: 1,
                    b: 1,
                    c: {
                        d: {
                            e: 100,
                        },
                    },
                },
            },
            computed: {
                info() {
                    return this.isHot ? "炎热" : "凉爽"
                }
            },
            methods: {
                changeWeather() {
                    this.isHot = !this.isHot;
                    this.x++;
                },
            },
            watch: {
                'number.a': {
                    handler(newValue, oldValue) {
                        console.log('a被改变了');
                    }
                },
                number: {
                    deep: true,
                    handler(newValue, oldValue) {
                        console.log('number', newValue, oldValue);
                    },
                }
            }
        });

    </script>
</body>

</html>